A focused ion beam system is applied to study the dose dependence of the shape of Ge channeling implantation profiles at two very different dose rates (1018 and 1011 cm-2 s-1), and for implantation temperatures of 250 °C and room temperature (RT). A simple model for the buildup of radiation damage is developed to describe the dechanneling effect of defects formed during ion bombardment. The use of this model in atomistic computer simulations yields Ge depth profiles which agree well with measured data. The lifetime of ion-beam-induced defects at 250 °C was estimated to be in the order of 100 s. At RT, some defect relaxation was found between 10 μs and 100 s after ion impact. © 2001 American Institute of Physics.